<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <!--html的注释-->
  <style>
    /*d*/
    h2{
        color:yellow;
    }
  </style>
    <link rel="stylesheet" href="my.css">
</head>
<body>

<h1 style="color: red">内联样式</h1>
<h2>内部样式1</h2>
<h2>内部样式2</h2>
<h3>外部样式3</h3>
</body>
</html>